Volume 38,Issue 6,2009 Table of Contents
2009, 38(6):941-946.
Abstract:
The electrode alloys La0.7Mg0.3Co0.45Ni2.55-xFex (x = 0, 0.1, 0.2, 0.3, 0.4) were prepared by casting and rapid quenching. The influences of the substitution of Fe for Ni on their cycle stabilities as well as their structures were investigated in detail. The results indicate that the substitution of Fe for Ni significantly improves the cycle stability of the alloys, and the positive impact of such a substitution on the cycle stability of the as-quenched alloy is much larger than that of the as-cast. All of the alloys have multiphase structures composed of two major phases, (La, Mg)Ni3 and LaNi5, and a residual phase LaNi2. The substitution of Fe for Ni helps the formation of a like amorphous structure in the as-quenched alloy. With the increase of Fe content, the grains in the as-quenched alloy are significantly refined, and the lattice constants and the cell volumes of the alloys are obviously enlarged.
The electrode alloys La0.7Mg0.3Co0.45Ni2.55-xFex (x = 0, 0.1, 0.2, 0.3, 0.4) were prepared by casting and rapid quenching. The influences of the substitution of Fe for Ni on their cycle stabilities as well as their structures were investigated in detail. The results indicate that the substitution of Fe for Ni significantly improves the cycle stability of the alloys, and the positive impact of such a substitution on the cycle stability of the as-quenched alloy is much larger than that of the as-cast. All of the alloys have multiphase structures composed of two major phases, (La, Mg)Ni3 and LaNi5, and a residual phase LaNi2. The substitution of Fe for Ni helps the formation of a like amorphous structure in the as-quenched alloy. With the increase of Fe content, the grains in the as-quenched alloy are significantly refined, and the lattice constants and the cell volumes of the alloys are obviously enlarged.
2009, 38(6):947-950.
Abstract:
In the Shell Coal Gasification Process (SCGP), porous stainless steel cone is used as a gas-distributor to make pulverized coal entering fluidization which can insure the continuous transportation of coal powder and improve the combustion efficiency. In the service conditions the porous cone must have not only high and uniform permeability, but also a proper strength. This study focuses on the preparation of porous stainless steel cone and tube with high performances such as permeability and strength etc. for applications. The porous cone/tube with 32%-35% in porosity, 20 micron in maximum pore size was prepared by CIP. After welding and sealing, the breaking pressures of cone/tube are larger than 2.5 MPa which meet the requirements for fluidization transportation of coal powder in SCGP.
In the Shell Coal Gasification Process (SCGP), porous stainless steel cone is used as a gas-distributor to make pulverized coal entering fluidization which can insure the continuous transportation of coal powder and improve the combustion efficiency. In the service conditions the porous cone must have not only high and uniform permeability, but also a proper strength. This study focuses on the preparation of porous stainless steel cone and tube with high performances such as permeability and strength etc. for applications. The porous cone/tube with 32%-35% in porosity, 20 micron in maximum pore size was prepared by CIP. After welding and sealing, the breaking pressures of cone/tube are larger than 2.5 MPa which meet the requirements for fluidization transportation of coal powder in SCGP.
2009, 38(6):951-954.
Abstract:
The Faraday rotation of Cd0.8Mn0.2Te and Cd0.9Mn0.1Te single crystals grown in our laboratory was measured at room temperature. We analyzed our Faraday rotation data in terms of a modified multi-oscillator model by improving the value of the band gap at L point in the Brillouin zone (E1) and obtained the values of the gap at the Γ point in the Brillouin zone (E0) for Cd0.8Mn0.2Te and Cd0.9Mn0.1Te from the fitting to 1.667 eV and 1.804 eV, respectively. The values of E0 are more close to the calculated ones than nearly all of the previous studies.
The Faraday rotation of Cd0.8Mn0.2Te and Cd0.9Mn0.1Te single crystals grown in our laboratory was measured at room temperature. We analyzed our Faraday rotation data in terms of a modified multi-oscillator model by improving the value of the band gap at L point in the Brillouin zone (E1) and obtained the values of the gap at the Γ point in the Brillouin zone (E0) for Cd0.8Mn0.2Te and Cd0.9Mn0.1Te from the fitting to 1.667 eV and 1.804 eV, respectively. The values of E0 are more close to the calculated ones than nearly all of the previous studies.
2009, 38(6):955-957.
Abstract:
The deformed microstructures and mechanical properties of commercial pure titanium (CP-Ti) with an initial grain size of about 28 μm was investigated using equal channel angular pressing (ECAP). ECAP was conducted at room temperature adopting a die with a channel angle of 120° via route BC. Special attention was paid on the microstructure evolution and mechanical properties of the ECAP samples. Deformation twins were found in most grains after the first and second pass of ECAP. After four ECAP passes, the original grains were refined from 28 μm to about 250 nm, and the ultimate strength and microhardness were significantly enhanced to 773 MPa and 2486 MPa, respectively. Meanwhile good ductility of 16.8% elongation still remained.
The deformed microstructures and mechanical properties of commercial pure titanium (CP-Ti) with an initial grain size of about 28 μm was investigated using equal channel angular pressing (ECAP). ECAP was conducted at room temperature adopting a die with a channel angle of 120° via route BC. Special attention was paid on the microstructure evolution and mechanical properties of the ECAP samples. Deformation twins were found in most grains after the first and second pass of ECAP. After four ECAP passes, the original grains were refined from 28 μm to about 250 nm, and the ultimate strength and microhardness were significantly enhanced to 773 MPa and 2486 MPa, respectively. Meanwhile good ductility of 16.8% elongation still remained.
2009, 38(6):958-961.
Abstract:
In this study, La62.0Al15.7(Cu0.5Ni0.5)22.3 bulk metallic glasses (BMGs) were prepared by copper mold casting method, and the effects of the pressure treatment up to 5.0 GPa at room temperature on structural relaxation were investigated by X-ray diffraction (XRD) and differential scanning calorimeter (DSC). The results showed that structural relaxation occurred with changes of the glass transition temperature (Tg) and the onset of primary crystallization (Tx1). Both increased with increasing of applied pressure up to 4.0 GPa beyond which they decreased. The enthalpy changed at the glass transition temperature regime showed that the reduction of the free volume caused by the HP treatment can be interpreted by the activation volumes of the flow defects. Furthermore, the HP treatment also influenced the crystallization sequence of the BMG.
In this study, La62.0Al15.7(Cu0.5Ni0.5)22.3 bulk metallic glasses (BMGs) were prepared by copper mold casting method, and the effects of the pressure treatment up to 5.0 GPa at room temperature on structural relaxation were investigated by X-ray diffraction (XRD) and differential scanning calorimeter (DSC). The results showed that structural relaxation occurred with changes of the glass transition temperature (Tg) and the onset of primary crystallization (Tx1). Both increased with increasing of applied pressure up to 4.0 GPa beyond which they decreased. The enthalpy changed at the glass transition temperature regime showed that the reduction of the free volume caused by the HP treatment can be interpreted by the activation volumes of the flow defects. Furthermore, the HP treatment also influenced the crystallization sequence of the BMG.
2009, 38(6):962-966.
Abstract:
Microscopic phase-field model was used to simulate the ordered domain interfaces formed between DO22 (Ni3V) phases along [100] and [001] direction in Ni-Al-V alloy. The atomic structure of the interface and the composition of alloying elements at the interfaces were investigated using the occupation probability of atoms. The results show that there are three kinds of stable interfaces formed between DO22 phases (Ni3V) along [100] and [001] direction, and all of them can not migrate. The property of interfaces is related to the atomic structure of interfaces. The L12 phases are precipitated at the (002)//(100) interfaces easily, and this kind of interfaces mainly exist at the early period of precipitation, the (002)//(100)·?[100] interface can form a kind of transitional interface at the early period of precipitation, while the {110} twin interface is the most stable and usual interface of the three kinds of interfaces. The elements of alloy have different preferences of segregation and depletion at different boundaries, V is depleted but Ni is segregated at all interfaces; Al is depleted at the (002)//(100)·?[100] interface but segregated at the other interfaces. The degrees of segregation and depletion are different at different interfaces.
Microscopic phase-field model was used to simulate the ordered domain interfaces formed between DO22 (Ni3V) phases along [100] and [001] direction in Ni-Al-V alloy. The atomic structure of the interface and the composition of alloying elements at the interfaces were investigated using the occupation probability of atoms. The results show that there are three kinds of stable interfaces formed between DO22 phases (Ni3V) along [100] and [001] direction, and all of them can not migrate. The property of interfaces is related to the atomic structure of interfaces. The L12 phases are precipitated at the (002)//(100) interfaces easily, and this kind of interfaces mainly exist at the early period of precipitation, the (002)//(100)·?[100] interface can form a kind of transitional interface at the early period of precipitation, while the {110} twin interface is the most stable and usual interface of the three kinds of interfaces. The elements of alloy have different preferences of segregation and depletion at different boundaries, V is depleted but Ni is segregated at all interfaces; Al is depleted at the (002)//(100)·?[100] interface but segregated at the other interfaces. The degrees of segregation and depletion are different at different interfaces.
2009, 38(6):967-971.
Abstract:
TiO2 nanotube arrays were prepared by anodic oxidation at a constant potential in organic electrolytes (NH4F/glycerol, NH4F/ethylene glycol). The effects of anodic potential, anodic time and electrolyte composition on the nanotube morphology were investigated. A growth mechanism of TiO2 nanotube arrays in organic electrolytes was proposed. The results indicated that a much wider range of anodic voltage and longer anodic time for the preparation of TiO2 nanotube arrays were required in organic electrolytes. Furthermore, TiO2 nanotube arrays with different morphologies could be fabricated in organic electrolytes with different water contents. The large coefficient of viscosity and the low oxygen content of the organic electrolytes improved the growth velocity of the nanotubes, at the same time controlled their corrosion velocity, resulting in forming longer nanotubes in the electrolytes. Since the growing velocity of nanotube arrays in NH4F/ethylene glycol was bigger than that in NH4F/glycerol, longer nanotubes (64 μm) could be obtained in NH4F/ethylene glycol.
TiO2 nanotube arrays were prepared by anodic oxidation at a constant potential in organic electrolytes (NH4F/glycerol, NH4F/ethylene glycol). The effects of anodic potential, anodic time and electrolyte composition on the nanotube morphology were investigated. A growth mechanism of TiO2 nanotube arrays in organic electrolytes was proposed. The results indicated that a much wider range of anodic voltage and longer anodic time for the preparation of TiO2 nanotube arrays were required in organic electrolytes. Furthermore, TiO2 nanotube arrays with different morphologies could be fabricated in organic electrolytes with different water contents. The large coefficient of viscosity and the low oxygen content of the organic electrolytes improved the growth velocity of the nanotubes, at the same time controlled their corrosion velocity, resulting in forming longer nanotubes in the electrolytes. Since the growing velocity of nanotube arrays in NH4F/ethylene glycol was bigger than that in NH4F/glycerol, longer nanotubes (64 μm) could be obtained in NH4F/ethylene glycol.
2009, 38(6):972-975.
Abstract:
The effects of process parameters, such as deformation temperature, strain, strain rate and cooling condition on structure parameters (b grain size D, a-colony size d, a-lamina thickness b), and the relationship between lamella structure parameters and mechanical properties were investigated during b field hot deformation for TA15 titanium alloy. A quantitative relationship between structure parameters and mechanical properties was presented by multi-element regress analysis, and the mechanical properties could be predict by using above mentioned relationship.
The effects of process parameters, such as deformation temperature, strain, strain rate and cooling condition on structure parameters (b grain size D, a-colony size d, a-lamina thickness b), and the relationship between lamella structure parameters and mechanical properties were investigated during b field hot deformation for TA15 titanium alloy. A quantitative relationship between structure parameters and mechanical properties was presented by multi-element regress analysis, and the mechanical properties could be predict by using above mentioned relationship.
2009, 38(6):976-981.
Abstract:
The purpose of the present study is to know the influences of thermo-mechanical processing and heat-treatment on the prior b-grain size of TC4 titanium alloy, and the influence of grain size on damage-tolerance properties is also discussed. The average b-grain sizes under different thermo-mechanical processing and solution treatment conditions were measured. Noticeable difference of b-grain growth behavior was found between α+b forged and b forged TC4 alloy under the same heat-treatment conditions. The exponential relationship between b-grain size and solution time was presented. The results show that b-grain size does not always increase with increasing of solution-treatment temperature; a limit value of the grain size will appear in certain temperature region. For different forging process, the fluctuation of the prior b -grain size is different. This phenomenon is discussed in terms of grain growth thermodynamics and kinetics laws. Damage-tolerance properties results show that grain size has noticeable influence on fatigue crack growth rate and fracture toughness property.
The purpose of the present study is to know the influences of thermo-mechanical processing and heat-treatment on the prior b-grain size of TC4 titanium alloy, and the influence of grain size on damage-tolerance properties is also discussed. The average b-grain sizes under different thermo-mechanical processing and solution treatment conditions were measured. Noticeable difference of b-grain growth behavior was found between α+b forged and b forged TC4 alloy under the same heat-treatment conditions. The exponential relationship between b-grain size and solution time was presented. The results show that b-grain size does not always increase with increasing of solution-treatment temperature; a limit value of the grain size will appear in certain temperature region. For different forging process, the fluctuation of the prior b -grain size is different. This phenomenon is discussed in terms of grain growth thermodynamics and kinetics laws. Damage-tolerance properties results show that grain size has noticeable influence on fatigue crack growth rate and fracture toughness property.
2009, 38(6):982-986.
Abstract:
Ti-Al-Nb based alloys were prepared by a non consumable skull melting. The effect of Al content on the microstructure and the solidification characterization of as-cast alloys were investigated using X-ray diffraction, optical microscope, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is shown that a fine grain structure Ti-44Al-2Nb-1Cr-1W-1B alloy with average grain size 50 mm could be got by proper decreasing of Al content, and the companion phenomenon of co-existence of b and g phases in the fine grain structure as-cast alloy was found. Moreover, the proper additions of alloying elements such as W and Nb increased the stability of b phase, and thus b phase was retained to low temperature. The presence of b phase was found to restrict a grain growth at the temperatures above the a transus temperature.
Ti-Al-Nb based alloys were prepared by a non consumable skull melting. The effect of Al content on the microstructure and the solidification characterization of as-cast alloys were investigated using X-ray diffraction, optical microscope, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is shown that a fine grain structure Ti-44Al-2Nb-1Cr-1W-1B alloy with average grain size 50 mm could be got by proper decreasing of Al content, and the companion phenomenon of co-existence of b and g phases in the fine grain structure as-cast alloy was found. Moreover, the proper additions of alloying elements such as W and Nb increased the stability of b phase, and thus b phase was retained to low temperature. The presence of b phase was found to restrict a grain growth at the temperatures above the a transus temperature.
11 Numerical Simulation for Keyhole Profile and Their Effect of TC4 Titanium Alloy during Laser Welding
2009, 38(6):987-990.
Abstract:
According to the characteristics of the existence of keyhole phenomena on TC4 titanium alloy during laser welding, a precise calculation model fitting to the keyhole size in micron dimension has been developed. Using the Gaussian rotating curved body heat source fitting for the keyhole profile and combining the material property of TC4 titanium alloy, the distribution characteristics of keyhole profile and transient welding temperature varying with the laser parameters have obtained. The greatest influences of laser welding parameters on keyhole profile of TC4 titanium alloy have been found out by analyzing the specificity size and temperature distribution in front and back edge of the keyhole and in radial and depth direction of the keyhole. The optimal range of laser welding parameters to obtain the best keyhole profile and temperature distribution of TC4 titanium alloy during laser welding has been found out by analyzing the influence of every welding parameter.
According to the characteristics of the existence of keyhole phenomena on TC4 titanium alloy during laser welding, a precise calculation model fitting to the keyhole size in micron dimension has been developed. Using the Gaussian rotating curved body heat source fitting for the keyhole profile and combining the material property of TC4 titanium alloy, the distribution characteristics of keyhole profile and transient welding temperature varying with the laser parameters have obtained. The greatest influences of laser welding parameters on keyhole profile of TC4 titanium alloy have been found out by analyzing the specificity size and temperature distribution in front and back edge of the keyhole and in radial and depth direction of the keyhole. The optimal range of laser welding parameters to obtain the best keyhole profile and temperature distribution of TC4 titanium alloy during laser welding has been found out by analyzing the influence of every welding parameter.
Zhou Xiaolong
,
Cao Jianchun
,
Chen Jingchao
,
Zhang Kunhua
,
Yu Jie
,
Du Yan
,
Geng Yonghong
,
Sun Jialing
,
Wu Daping
2009, 38(6):991-994.
Abstract:
The microstructure homogenizations of AgSnO2, AgCuO and AgY2O3 electric contact materials prepared by reactive synthesis process and severe plastic deformation process were investigated. The result showed that the microstructures of the three electric contact materials were different under the same process conditions. The main reason of the above mentioned results is attributed to different diffusion mechanisms which are caused by different element natures in the alloy system. The microstructures of the three electric contact materials can be homogenized by severe plastic deformation, Fore the different electric contact material systems, different plastic deformation degrees are required.
The microstructure homogenizations of AgSnO2, AgCuO and AgY2O3 electric contact materials prepared by reactive synthesis process and severe plastic deformation process were investigated. The result showed that the microstructures of the three electric contact materials were different under the same process conditions. The main reason of the above mentioned results is attributed to different diffusion mechanisms which are caused by different element natures in the alloy system. The microstructures of the three electric contact materials can be homogenized by severe plastic deformation, Fore the different electric contact material systems, different plastic deformation degrees are required.
2009, 38(6):995-998.
Abstract:
The effects of the doping elements such as La and F on the phase structure, the morphology, the activate and electrochemical properties of the spinel LiMn2O4 cathode material prepared by high temperature solid state reaction were investigated by means of the X-ray diffraction (XRD), scanning electron microscope (SEM) and battery testing system this paper. The results showed that the initial discharge capacity of the LiMn2O4-xFx sample decreased, and the cyclic stability of the specimen increased and then decreased with increasing of the content of the replacement elements Fluorine. The capacity ratio of discharge to charge and the cyclic stability of the LiMn2O4 sample were improved with the manganese and Oxygen partial replaced by La and F, respectively. The LiLayMn2-yO4-xFx sample was composed of single-phase spinel LiMn2O4 when the content of the doping elements La and F was minor, the particles of the specimen were spheroid or sphere, and the sizes of the particles were 0.5~2.5 μm. The discharge-capacity of the LiLa0.02Mn1.98O3.95F0.05 sample was 123.6 mAh/g and 114.6 mAh/g after the first and the 30th charge/discharge cycles, respectively.
The effects of the doping elements such as La and F on the phase structure, the morphology, the activate and electrochemical properties of the spinel LiMn2O4 cathode material prepared by high temperature solid state reaction were investigated by means of the X-ray diffraction (XRD), scanning electron microscope (SEM) and battery testing system this paper. The results showed that the initial discharge capacity of the LiMn2O4-xFx sample decreased, and the cyclic stability of the specimen increased and then decreased with increasing of the content of the replacement elements Fluorine. The capacity ratio of discharge to charge and the cyclic stability of the LiMn2O4 sample were improved with the manganese and Oxygen partial replaced by La and F, respectively. The LiLayMn2-yO4-xFx sample was composed of single-phase spinel LiMn2O4 when the content of the doping elements La and F was minor, the particles of the specimen were spheroid or sphere, and the sizes of the particles were 0.5~2.5 μm. The discharge-capacity of the LiLa0.02Mn1.98O3.95F0.05 sample was 123.6 mAh/g and 114.6 mAh/g after the first and the 30th charge/discharge cycles, respectively.
2009, 38(6):999-1004.
Abstract:
The Co48Cr15Mo14C15B6Er2 amorphous ribbon and rods with diameters of 2mm and 7mm were prepared by melt spinning and copper mold casting. The different Scanning calorimetry and the vibrating sample magnetometer were employed to investigate the effect of cooling rate on crystallization kinetics and magnetic properties of metallic Co48Cr15Mo14C15B6Er2 glass. It was found that the cooling rate had significant influence on the crystallization kinetics. In the case of non-isothermal crystallization process, the glass transition temperature and the activation energy for the glass transition decreased with decreasing of cooling rate. The activation energy for crystallization also decreased with decreasing of cooling rate, in despite of that the peak temperature of crystallization was independent of cooling rate. Although the isothermal crystallization was governed by diffusion-controlled three-dimensional growth with decreasing of nucleation rate for Co48Cr15Mo14C15B6Er2 glasses under different cooling rates, how rapidly the nucleation rate decreased was related to cooling rate. The more rapid the cooling rate was, the faster the decrease of the rate was. The magnetic properties of Co48Cr15Mo14C15B6Er2 glass was significantly affected by cooling rate. The sample obtained at high cooling rate took on paramagnetic property, whereas the sample obtained at low cooling rate took on ferromagnetic property. The saturation magnetization increased with decreasing of cooling rate.
The Co48Cr15Mo14C15B6Er2 amorphous ribbon and rods with diameters of 2mm and 7mm were prepared by melt spinning and copper mold casting. The different Scanning calorimetry and the vibrating sample magnetometer were employed to investigate the effect of cooling rate on crystallization kinetics and magnetic properties of metallic Co48Cr15Mo14C15B6Er2 glass. It was found that the cooling rate had significant influence on the crystallization kinetics. In the case of non-isothermal crystallization process, the glass transition temperature and the activation energy for the glass transition decreased with decreasing of cooling rate. The activation energy for crystallization also decreased with decreasing of cooling rate, in despite of that the peak temperature of crystallization was independent of cooling rate. Although the isothermal crystallization was governed by diffusion-controlled three-dimensional growth with decreasing of nucleation rate for Co48Cr15Mo14C15B6Er2 glasses under different cooling rates, how rapidly the nucleation rate decreased was related to cooling rate. The more rapid the cooling rate was, the faster the decrease of the rate was. The magnetic properties of Co48Cr15Mo14C15B6Er2 glass was significantly affected by cooling rate. The sample obtained at high cooling rate took on paramagnetic property, whereas the sample obtained at low cooling rate took on ferromagnetic property. The saturation magnetization increased with decreasing of cooling rate.
2009, 38(6):1005-1009.
Abstract:
Rapidly solidified microstructure of a laser surface remelted TA15 titanium alloy as a function of laser scanning speed and solidification cooling rate was investigated. Abnormal coarsening of b grains in the rapidly solidified remelted zone was readily observed for the laser glazed TA15 titanium alloy irrespective of the rapid solidification cooling rate. The b grains in laser remelted zone of TA15 titanium alloy were abnormally coarsened and their sizes were up to 10 to 20 times larger than that of the a grains or 32 to 62 times larger than that of the b grains in the original material. The rapid solidification and grain growth of molten bath of laser surface remelting TA15 titanium alloy was a process of directly epitaxial growth of the b grains of the unmelted substrate at the contact of the melt-pool bottom. The rapidly solidified b grain size in the laser remelted zone was determined by the b grain size of unmelted base metal at the bottom of molten bath. During laser heating and molten bath forming in the surface of the TA15 titanium alloy, b grains of the unmelted base metal at the top of heat-affected zone nucleated, grew in an extremely short time owing to the extremely high temperature. Solid-state abnormal coarsening of b grains on the unmelted base metal at the bottom of molten bath resulted in the abnormal coarsening of rapidly solidification structure in laser remelted zone of the TA15 titanium alloy.
Rapidly solidified microstructure of a laser surface remelted TA15 titanium alloy as a function of laser scanning speed and solidification cooling rate was investigated. Abnormal coarsening of b grains in the rapidly solidified remelted zone was readily observed for the laser glazed TA15 titanium alloy irrespective of the rapid solidification cooling rate. The b grains in laser remelted zone of TA15 titanium alloy were abnormally coarsened and their sizes were up to 10 to 20 times larger than that of the a grains or 32 to 62 times larger than that of the b grains in the original material. The rapid solidification and grain growth of molten bath of laser surface remelting TA15 titanium alloy was a process of directly epitaxial growth of the b grains of the unmelted substrate at the contact of the melt-pool bottom. The rapidly solidified b grain size in the laser remelted zone was determined by the b grain size of unmelted base metal at the bottom of molten bath. During laser heating and molten bath forming in the surface of the TA15 titanium alloy, b grains of the unmelted base metal at the top of heat-affected zone nucleated, grew in an extremely short time owing to the extremely high temperature. Solid-state abnormal coarsening of b grains on the unmelted base metal at the bottom of molten bath resulted in the abnormal coarsening of rapidly solidification structure in laser remelted zone of the TA15 titanium alloy.
2009, 38(6):1010-1014.
Abstract:
Novel corrosive wear resistant alloys with the microstructure consisting of ternary metal silicide Ti2Ni3Si primary dendrites and Ti2Ni3Si/NiTi eutectic matrix were designed and fabricated by the laser melting process. Both the corrosion behavior of Ti2Ni3Si/NiTi intermetallic alloys and the effect of Ti content in alloys on the corrosion resistance of alloys were investigated by polarization curve, Tafel plot, EIS in 1 mol/L H2SO4 solution. Results show that the alloys have excellent corrosion resistance in 1 mol/L H2SO4 solution owing to the formation of stable passivation film and the high chemical stability of Ti2Ni3Si and NiTi intermetallic. With increasing of Ti content, the corrosion resistances of the alloys are improved slightly.
Novel corrosive wear resistant alloys with the microstructure consisting of ternary metal silicide Ti2Ni3Si primary dendrites and Ti2Ni3Si/NiTi eutectic matrix were designed and fabricated by the laser melting process. Both the corrosion behavior of Ti2Ni3Si/NiTi intermetallic alloys and the effect of Ti content in alloys on the corrosion resistance of alloys were investigated by polarization curve, Tafel plot, EIS in 1 mol/L H2SO4 solution. Results show that the alloys have excellent corrosion resistance in 1 mol/L H2SO4 solution owing to the formation of stable passivation film and the high chemical stability of Ti2Ni3Si and NiTi intermetallic. With increasing of Ti content, the corrosion resistances of the alloys are improved slightly.
2009, 38(6):1019-1024.
Abstract:
The multi-objective optimization was studied using response surface method (RSM) and FEM simulation for a preform design of aeroengine disk forging. Firstly, taking the deformation homogeneity within forgings and die filling completeness as the objective, a reduced quadratic model was developed through regression analysis and ANOVA (analysis of variance), and then the optimal results are obtained and discussed. Secondly, redesign and optimization were carried out to reduce the deformation load on the basis of the former optimization results. The results show that RSM is an effective and flexible method to realize multi-objective preform optimization design for hard deformed material forging.
The multi-objective optimization was studied using response surface method (RSM) and FEM simulation for a preform design of aeroengine disk forging. Firstly, taking the deformation homogeneity within forgings and die filling completeness as the objective, a reduced quadratic model was developed through regression analysis and ANOVA (analysis of variance), and then the optimal results are obtained and discussed. Secondly, redesign and optimization were carried out to reduce the deformation load on the basis of the former optimization results. The results show that RSM is an effective and flexible method to realize multi-objective preform optimization design for hard deformed material forging.
2009, 38(6):1025-1028.
Abstract:
The hot compressive deformation behaviour of high Nb containing TiAl alloy was investigated in the temperature range of 900~1250 ℃, at the strain rate range of 5×10-4 ~1 s-1 and the engineering strain range of 50%~80% on Gleeble-1500 hot simulator. The flow stress behaviour of high Nb containing TiAl alloy can be represented by a Zener-Hollomon parameter in the exponent style equation. The regressed expression is σp=197.6ln{(Z/9.59×1015)0.285+(Z/9.59×1015)0.570+1}1/2}. The hot deformation activation energy of high Nb containing TiAl alloy during hot deformation is (497±49) kJ/mol. The hot deformability map of cast high Nb containing TiAl alloy was given in this paper.
The hot compressive deformation behaviour of high Nb containing TiAl alloy was investigated in the temperature range of 900~1250 ℃, at the strain rate range of 5×10-4 ~1 s-1 and the engineering strain range of 50%~80% on Gleeble-1500 hot simulator. The flow stress behaviour of high Nb containing TiAl alloy can be represented by a Zener-Hollomon parameter in the exponent style equation. The regressed expression is σp=197.6ln{(Z/9.59×1015)0.285+(Z/9.59×1015)0.570+1}1/2}. The hot deformation activation energy of high Nb containing TiAl alloy during hot deformation is (497±49) kJ/mol. The hot deformability map of cast high Nb containing TiAl alloy was given in this paper.
19 Influence of Heat Treatment on Mechanical and Damping Properties of As-Extruded ZK60 Magnesium Alloy
2009, 38(6):1029-1032.
Abstract:
The microstructure, mechanical and damping properties of ZK60 magnesium alloy in the solution treatment, ageing treatment and solution-ageing treatment states were investigated by using the optical microscope, tensile test and dynamic mechanical analyzer. The results show that the three heat treatments have some influences on the ultimate strength, the yield strength and the elongation of ZK60 magnesium alloys, and improve their damping properties to some extent. The influences of heat treatment technology on damping properties can be explained by the G-L theory.
The microstructure, mechanical and damping properties of ZK60 magnesium alloy in the solution treatment, ageing treatment and solution-ageing treatment states were investigated by using the optical microscope, tensile test and dynamic mechanical analyzer. The results show that the three heat treatments have some influences on the ultimate strength, the yield strength and the elongation of ZK60 magnesium alloys, and improve their damping properties to some extent. The influences of heat treatment technology on damping properties can be explained by the G-L theory.
2009, 38(6):1033-1037.
Abstract:
The stable precursor slurry of indium-tin-oxide (ITO) was prepared using metal In and crystalloid tin tetrachloride as raw materials by adding different additives. The effect of dispersants on the stability of ITO precursor slurry was studied by Zeta potential value, TEM and sediment. The influences of pH value and dispersant content on stability of the slurry were investigated. And the effects of the different dispersant and their dispersing mechanism on the stability of the slurry were also investigated. The results show that a higher electrostatic effect could be obtained by adjusting pH value of medium and adding ionic dispersant. Based on the above mentioned, non-ionic surfactants (PEG, PVP) were added, resulting in creating a steric hindered effect among particles, which prevented the agglomeration of the particles so as to obtain a high dispersed and steady slurry. The particle sizes of the slurry were about 10~20 nm. The following finding can be drawn from the experiment that the optimum contents of dispersants are PEG 10% and monoethanolamine 2.5% (mass fraction).
The stable precursor slurry of indium-tin-oxide (ITO) was prepared using metal In and crystalloid tin tetrachloride as raw materials by adding different additives. The effect of dispersants on the stability of ITO precursor slurry was studied by Zeta potential value, TEM and sediment. The influences of pH value and dispersant content on stability of the slurry were investigated. And the effects of the different dispersant and their dispersing mechanism on the stability of the slurry were also investigated. The results show that a higher electrostatic effect could be obtained by adjusting pH value of medium and adding ionic dispersant. Based on the above mentioned, non-ionic surfactants (PEG, PVP) were added, resulting in creating a steric hindered effect among particles, which prevented the agglomeration of the particles so as to obtain a high dispersed and steady slurry. The particle sizes of the slurry were about 10~20 nm. The following finding can be drawn from the experiment that the optimum contents of dispersants are PEG 10% and monoethanolamine 2.5% (mass fraction).
2009, 38(6):1038-1042.
Abstract:
The formation and decomposition of MC carbides in alloys with different contents of Re and Ta were investigated by DSC, SEM, EDS and XRD. The results show that script MC carbides in three alloys was formed by eutectic solidification. The addition of Ta not only decreased the W concentration but also minimized the difference of W composition in MC carbides formed at difference freezing period in three alloys. Meanwhile, the addition of Ta also increased the formation temperature and the thermal stability of MC phase significantly. Re was not found in MC carbides. The addition of Re slightly decreased the formation temperature of MC carbides and promoted the precipitation of μ phase from the oversaturated γ matrix.
The formation and decomposition of MC carbides in alloys with different contents of Re and Ta were investigated by DSC, SEM, EDS and XRD. The results show that script MC carbides in three alloys was formed by eutectic solidification. The addition of Ta not only decreased the W concentration but also minimized the difference of W composition in MC carbides formed at difference freezing period in three alloys. Meanwhile, the addition of Ta also increased the formation temperature and the thermal stability of MC phase significantly. Re was not found in MC carbides. The addition of Re slightly decreased the formation temperature of MC carbides and promoted the precipitation of μ phase from the oversaturated γ matrix.
2009, 38(6):1043-1047.
Abstract:
60vol %Carbon fiber reinforced magnesium matrix composites were fabricated by pressure infiltration method. The coefficient of thermal expansion measurement of carbon fiber reinforced magnesium matrix composites were carried out on a dilatometer 402C at the temperature ranged at 20~300 ℃. The relations among α and heat treatment condition, elastic modulus of the fibers and yield strength of matrix alloys were investigated. Results showed that α of the composites decreased with increasing of elastic modulus of fibers and reducing of yield strength for matrix alloys. Moreover, the α of composites decreased after annealing treatment. In this paper, the estimate formula of the α in transverse direction of composites is presented, and this calculation method should minimize the error between the calculation value and the true value. The model for laminate structure composite α in 2D planar is suggested, and the α of [0/±15/±30/±45/±60/±75/±90]S laminates are isotropy.
60vol %Carbon fiber reinforced magnesium matrix composites were fabricated by pressure infiltration method. The coefficient of thermal expansion measurement of carbon fiber reinforced magnesium matrix composites were carried out on a dilatometer 402C at the temperature ranged at 20~300 ℃. The relations among α and heat treatment condition, elastic modulus of the fibers and yield strength of matrix alloys were investigated. Results showed that α of the composites decreased with increasing of elastic modulus of fibers and reducing of yield strength for matrix alloys. Moreover, the α of composites decreased after annealing treatment. In this paper, the estimate formula of the α in transverse direction of composites is presented, and this calculation method should minimize the error between the calculation value and the true value. The model for laminate structure composite α in 2D planar is suggested, and the α of [0/±15/±30/±45/±60/±75/±90]S laminates are isotropy.
2009, 38(6):1048-1052.
Abstract:
A new method for assessing the local shear strain in adiabatic shear band (ASB) of Ti-6Al-4V is proposed by using of gradient-dependent plasticity. The maximum local plastic shear strain (MLPSS) in the ASB depends on the critical plastic shear strain, the gage length of Ti-6Al-4V specimen, the total thickness of the ASB and the average plastic shear strain in the ASB. Results show that the MLPSS in the ASB decreases nonlinearly with the increase of the total thickness of the ASB. When the total thickness of the ASB approaches 1mm, although the methods for determining the critical plastic shear strain are different, the calculated values for MLPSSs in the ASB almost remain unchanged. When the total thickness of the ASB is in the range of 0.335~1 mm, the calculated values for MLPSSs in the ASB are found to be in the range of the lower bound (75%) to the upper bound (350%) of the experimental results obtained by Liao and Duffy (1998).
A new method for assessing the local shear strain in adiabatic shear band (ASB) of Ti-6Al-4V is proposed by using of gradient-dependent plasticity. The maximum local plastic shear strain (MLPSS) in the ASB depends on the critical plastic shear strain, the gage length of Ti-6Al-4V specimen, the total thickness of the ASB and the average plastic shear strain in the ASB. Results show that the MLPSS in the ASB decreases nonlinearly with the increase of the total thickness of the ASB. When the total thickness of the ASB approaches 1mm, although the methods for determining the critical plastic shear strain are different, the calculated values for MLPSSs in the ASB almost remain unchanged. When the total thickness of the ASB is in the range of 0.335~1 mm, the calculated values for MLPSSs in the ASB are found to be in the range of the lower bound (75%) to the upper bound (350%) of the experimental results obtained by Liao and Duffy (1998).
2009, 38(6):1053-1057.
Abstract:
The microstructures, the surface morphology and the composition of nanocrystalline Ni and nanocrystalline Ni-Co alloy prepared by pulse electrodeposition have been studied by XRD, SEM and EDS. The corrosion behaviors of nanocrystalline nickel and Ni-Co alloys in the solutions containing 305% (mass fraction) NaCl and 5% (mass fraction) were investigated by soak method and electrochemical polarization method respectively. The experimental results indicate that typical nanocrystalline nickel and Ni-Co alloy coatings can be synthesized by pulse electrodeposition, and the alloying element Co had an effect of solution strengthening and grain size refinement. The nanocrystalline Ni-Co alloy is dense in nature and it exhibited better corrosion resistance in 3.5% (mass fraction) NaCl solution and 5% (mass fraction) HCl solution than the nanocrystalline nickel. The surface morphology of all samples after corrosion in 3.5% (mass fraction) NaCl solution show good corrosion resistance, however, the samples were uniformly corroded in 5% (mass fraction) HCl solution.
The microstructures, the surface morphology and the composition of nanocrystalline Ni and nanocrystalline Ni-Co alloy prepared by pulse electrodeposition have been studied by XRD, SEM and EDS. The corrosion behaviors of nanocrystalline nickel and Ni-Co alloys in the solutions containing 305% (mass fraction) NaCl and 5% (mass fraction) were investigated by soak method and electrochemical polarization method respectively. The experimental results indicate that typical nanocrystalline nickel and Ni-Co alloy coatings can be synthesized by pulse electrodeposition, and the alloying element Co had an effect of solution strengthening and grain size refinement. The nanocrystalline Ni-Co alloy is dense in nature and it exhibited better corrosion resistance in 3.5% (mass fraction) NaCl solution and 5% (mass fraction) HCl solution than the nanocrystalline nickel. The surface morphology of all samples after corrosion in 3.5% (mass fraction) NaCl solution show good corrosion resistance, however, the samples were uniformly corroded in 5% (mass fraction) HCl solution.
2009, 38(6):1058-1061.
Abstract:
The stress-strain curve of (α + β) Ti-8Mn alloys was measured, and α and β titanium alloys, whose compositions were close to those of α and β phase in the dual phase titanium alloy (Ti-8Mn) were designed. According to the above mentioned design, the stress-strain curve of Ti-8Mn alloy was calculated and compared with measuring one. The results show that they are in good agreement, which indicates that the model established is available. According to the model above, the distributions of stress and strain were simulated along different sections when only one α grain was distributed in the β crystal. And the result illustrates that the minimum stress exists at the center of α crystalline grain, while the maximum stress exists at the crystal boundary. The stress decreases gradually with increasing of the distance away to dual sides, while the distribution of strain is in opposition to the stress distribution.
The stress-strain curve of (α + β) Ti-8Mn alloys was measured, and α and β titanium alloys, whose compositions were close to those of α and β phase in the dual phase titanium alloy (Ti-8Mn) were designed. According to the above mentioned design, the stress-strain curve of Ti-8Mn alloy was calculated and compared with measuring one. The results show that they are in good agreement, which indicates that the model established is available. According to the model above, the distributions of stress and strain were simulated along different sections when only one α grain was distributed in the β crystal. And the result illustrates that the minimum stress exists at the center of α crystalline grain, while the maximum stress exists at the crystal boundary. The stress decreases gradually with increasing of the distance away to dual sides, while the distribution of strain is in opposition to the stress distribution.
2009, 38(6):1062-1065.
Abstract:
The behaviour and mechanism of extraction of platinum (IV) with unsymmetrical sulfoxide BSO from HCl media are studied. The results showed that the percentage extraction of Pt (IV) achieved 99.55% from 4 mol·L-1 HCl media with 0.5 mol·L-1 BSO-kerosene as an extractant. This was an exothermic reaction with an enthalpy of –12.35 kJ·mol-1. The structure of complex was discussed by slope analysis method, UV spectra, FT-IR spectra. The extraction mechanism under the above mentioned conditions could be determined to be an ion-pair formation with the protonated BSO, and the composition of complex may be [2(BSOH+)]·[PtCl62-]·[BSO·HCl]·[2BSO](0).
The behaviour and mechanism of extraction of platinum (IV) with unsymmetrical sulfoxide BSO from HCl media are studied. The results showed that the percentage extraction of Pt (IV) achieved 99.55% from 4 mol·L-1 HCl media with 0.5 mol·L-1 BSO-kerosene as an extractant. This was an exothermic reaction with an enthalpy of –12.35 kJ·mol-1. The structure of complex was discussed by slope analysis method, UV spectra, FT-IR spectra. The extraction mechanism under the above mentioned conditions could be determined to be an ion-pair formation with the protonated BSO, and the composition of complex may be [2(BSOH+)]·[PtCl62-]·[BSO·HCl]·[2BSO](0).
2009, 38(6):1066-1070.
Abstract:
A new method of directly charging active metal nano-particles was developed so as to be used to improve the efficiency of depositing precious metals in catalytic layer. The precursors of active material were impregnated in porous carbon black layer in advance, and Pt or Pt alloy were firstly deposited on the surfaces of carbon black nearby Nafion particles by the pulse electro-deposition method. The performances of the electrodes were characterized by CV, and the structure and composition of deposited nano-particles by XRD, TEM and EDS. The optimum condition of the preparing process is toff /ton=300:100, wPtRu/wC=40% (mass fraction), nPt:nRu=1:1 (atom ratio). The specific surface is 92 m2/g, particle size 3.2 nm. Methanol peak value of current density reaches 82 mA·cm-2. The efficiency of Pt-M in porous catalytic layers is much higher than that of thin film electrode method, reaching about 79.1%.
A new method of directly charging active metal nano-particles was developed so as to be used to improve the efficiency of depositing precious metals in catalytic layer. The precursors of active material were impregnated in porous carbon black layer in advance, and Pt or Pt alloy were firstly deposited on the surfaces of carbon black nearby Nafion particles by the pulse electro-deposition method. The performances of the electrodes were characterized by CV, and the structure and composition of deposited nano-particles by XRD, TEM and EDS. The optimum condition of the preparing process is toff /ton=300:100, wPtRu/wC=40% (mass fraction), nPt:nRu=1:1 (atom ratio). The specific surface is 92 m2/g, particle size 3.2 nm. Methanol peak value of current density reaches 82 mA·cm-2. The efficiency of Pt-M in porous catalytic layers is much higher than that of thin film electrode method, reaching about 79.1%.
2009, 38(6):1071-1075.
Abstract:
Dense and uniform HA/ZrO2 composite coatings were prepared on biomedical titanium surfaces by Pulsed Electrochemical Deposition. The composite coatings were deposited in the form of ions and ZrO2 was uniformly dispersed in the composite coatings. The pulse potential with –3.5 V was beneficial to ion deposition recrystallization, to composite coating deposition. The compositions, structures, morphologies and bioactivity were characterized. The results showed that the coating compositions included hydroxyapatite (HA), octacalcium phosphate (OCP) and alkaline zirconium nitrate after electrodeposition and then they transformed into HA/ZrO2 composite coatings after high temperature sintering. Simulated body fluid immersion test proved that the as-prepared composite coatings had good bioactivity to induce calcium phosphate under simulated physiological environment.
Dense and uniform HA/ZrO2 composite coatings were prepared on biomedical titanium surfaces by Pulsed Electrochemical Deposition. The composite coatings were deposited in the form of ions and ZrO2 was uniformly dispersed in the composite coatings. The pulse potential with –3.5 V was beneficial to ion deposition recrystallization, to composite coating deposition. The compositions, structures, morphologies and bioactivity were characterized. The results showed that the coating compositions included hydroxyapatite (HA), octacalcium phosphate (OCP) and alkaline zirconium nitrate after electrodeposition and then they transformed into HA/ZrO2 composite coatings after high temperature sintering. Simulated body fluid immersion test proved that the as-prepared composite coatings had good bioactivity to induce calcium phosphate under simulated physiological environment.
2009, 38(6):1080-1083.
Abstract:
Ni microgrid transparent electrodes with different pore sizes (1.2，2.4，3.4，4.5 and 5.6 μm), were prepared via sputtering Ni into the gaps of PS colloidal crystal templates by magnetron sputtering. The influence of the pore sizes on the transmittance and the electric properties of the Ni microgrid transparent electrodes were investigated by SEM, UV-Vis spectrometer and four-point probe. It was found that the transmittance decreased and electric properties increased with the increase of the pore sizes of the samples. Ni microgrid transparent electrode showed a low electrical resistance and high transmittance in the ultraviolet-visible range. The results of theoretical calculation and AFM analysis indicated that the height of microgrid increased with the increase of the diameter of PS particles, which is the fundamental reason for the decrease of the transmission properties and the increase of electric properties of Ni microgrid transparent electrodes.
Ni microgrid transparent electrodes with different pore sizes (1.2，2.4，3.4，4.5 and 5.6 μm), were prepared via sputtering Ni into the gaps of PS colloidal crystal templates by magnetron sputtering. The influence of the pore sizes on the transmittance and the electric properties of the Ni microgrid transparent electrodes were investigated by SEM, UV-Vis spectrometer and four-point probe. It was found that the transmittance decreased and electric properties increased with the increase of the pore sizes of the samples. Ni microgrid transparent electrode showed a low electrical resistance and high transmittance in the ultraviolet-visible range. The results of theoretical calculation and AFM analysis indicated that the height of microgrid increased with the increase of the diameter of PS particles, which is the fundamental reason for the decrease of the transmission properties and the increase of electric properties of Ni microgrid transparent electrodes.
2009, 38(6):1084-1086.
Abstract:
Fabrication of Zirconia Nanotube Arrays by Anodization
Fabrication of Zirconia Nanotube Arrays by Anodization
2009, 38(6):1087-1090.
Abstract:
The effects of polyethylene imine on the corrosion of electroless nickel substrates during immersion gold plating were investigated by XRF, SEM and XPS in combination with open-circuit potential, polarization curves, electrochemical impedance spectrum and infrared (IR) reflection spectrum analysis. The results show that the polyethylene imine decreases the initial deposition rate while it has little effect on the longer deposition rate. The polyethylene imine decreases the concentrations of Ni and O in the gold coating. Moreover, it is also revealed that this additive could be adsorbed on the nickel or gold surface, and the adsorption on gold surface is stronger than that on nickel. The polyethylene imine improves the dissolution of the passivating film which is formed on the surface of the substrate and reduces the difference between activity/passivity of adjacent features of the surface. As a result, in the presence of this agent, the localized dissolution of nickel will be reduced and nickel contained in the substrate composition will be dissolved almost uniformly.
The effects of polyethylene imine on the corrosion of electroless nickel substrates during immersion gold plating were investigated by XRF, SEM and XPS in combination with open-circuit potential, polarization curves, electrochemical impedance spectrum and infrared (IR) reflection spectrum analysis. The results show that the polyethylene imine decreases the initial deposition rate while it has little effect on the longer deposition rate. The polyethylene imine decreases the concentrations of Ni and O in the gold coating. Moreover, it is also revealed that this additive could be adsorbed on the nickel or gold surface, and the adsorption on gold surface is stronger than that on nickel. The polyethylene imine improves the dissolution of the passivating film which is formed on the surface of the substrate and reduces the difference between activity/passivity of adjacent features of the surface. As a result, in the presence of this agent, the localized dissolution of nickel will be reduced and nickel contained in the substrate composition will be dissolved almost uniformly.
2009, 38(6):1091-1095.
Abstract:
Oxidant was prepared by the method of electrochemistry in situ leaching gold from refractory gold ores under the ultrasonic-aided and un-ultrasonic-aided conditions. Result show that the application of ultrasonic condition greatly increases the leaching rate and shortens the reaction time while the conventional cyanide method is adopted, the gold leaching rate after leaching 24 h is only 25% of the refractory gold ores. In the equal conditions, under the un-ultrasonic-aided in situ leaching conditions the leaching rate is 54.84% after leaching 6 h, whereas under the ultrasonic conditions the leaching rate grows to 90.68% after leaching 6 h. Otherwise, through comparison the X-ray diffraction patterns of ores and slag it is found that there exists element sulfur on the surface of un-ultrasonic-aided electro-chlorination leaching slag, and no sulfur on ultrasonic surface of the slag. And the effect of ultrasonic-aided condition on the electrode reaction and the mechanism of ultrasonic-aided leaching gold from refractory gold ores are analyzed.
Oxidant was prepared by the method of electrochemistry in situ leaching gold from refractory gold ores under the ultrasonic-aided and un-ultrasonic-aided conditions. Result show that the application of ultrasonic condition greatly increases the leaching rate and shortens the reaction time while the conventional cyanide method is adopted, the gold leaching rate after leaching 24 h is only 25% of the refractory gold ores. In the equal conditions, under the un-ultrasonic-aided in situ leaching conditions the leaching rate is 54.84% after leaching 6 h, whereas under the ultrasonic conditions the leaching rate grows to 90.68% after leaching 6 h. Otherwise, through comparison the X-ray diffraction patterns of ores and slag it is found that there exists element sulfur on the surface of un-ultrasonic-aided electro-chlorination leaching slag, and no sulfur on ultrasonic surface of the slag. And the effect of ultrasonic-aided condition on the electrode reaction and the mechanism of ultrasonic-aided leaching gold from refractory gold ores are analyzed.
2009, 38(6):1096-1099.
Abstract:
Ni-P coatings were deposited on sintered Nd-Fe-B magnets through the addition of Nd3+ in the electroless plating solution. The effects of Nd3+ concentration on the adhesion and corrosion resistance of the coatings were investigated. The adhesions between the magnets and the Ni-P coatings were measured in different Nd+ concentration plating solutions, and the polarization curves of the coatings in 3.5% (mass fraction) NaCl solution were plotted, the magnet corrosion resistances were characterized by neutral salt spray experiment. The results showed that the addition of Nd3+ could significantly improve the adhesion and corrosion resistance of Ni-P coatings on magnets. When increasing Nd3+ up to 2.5 g·L-1, the adhesion strength of the Ni-P coating to Nd-Fe-B magnet was enhanced from 6.4 to 25.2 MPa. Synchronously, the corrosion potential Ecorr of the coated magnets in 3.5% NaCl solution increased from －0.382 to －0.148 V, the corrosion current density Icorr decreased from 4.52 to 0.07 μA·cm-2, and the coated magnets could be as long as 256 h free of corrosion in the neutral salt spray, reflecting the improvement of corrosion resistance.
Ni-P coatings were deposited on sintered Nd-Fe-B magnets through the addition of Nd3+ in the electroless plating solution. The effects of Nd3+ concentration on the adhesion and corrosion resistance of the coatings were investigated. The adhesions between the magnets and the Ni-P coatings were measured in different Nd+ concentration plating solutions, and the polarization curves of the coatings in 3.5% (mass fraction) NaCl solution were plotted, the magnet corrosion resistances were characterized by neutral salt spray experiment. The results showed that the addition of Nd3+ could significantly improve the adhesion and corrosion resistance of Ni-P coatings on magnets. When increasing Nd3+ up to 2.5 g·L-1, the adhesion strength of the Ni-P coating to Nd-Fe-B magnet was enhanced from 6.4 to 25.2 MPa. Synchronously, the corrosion potential Ecorr of the coated magnets in 3.5% NaCl solution increased from －0.382 to －0.148 V, the corrosion current density Icorr decreased from 4.52 to 0.07 μA·cm-2, and the coated magnets could be as long as 256 h free of corrosion in the neutral salt spray, reflecting the improvement of corrosion resistance.
2009, 38(6):1100-1103.
Abstract:
V2.46TiFe0.54 alloy granules and Ni powder were mixed and pressed into electrodes greens, which were sintered at 850~1100 ℃ for 5 min. The influences of sinter temperature on the morphology and the electrochemical properties of the sintered V2.46TiFe0.54-Ni electrodes were investigated. XRD and SEM (EDS) analysises show that the V, Ti and Ni elements interdiffuse between the granules and Ni powders took places, resulting in forming a diffusing interlayer, its thickness increased with raising of the sintering temperature. The alloy granule surfaces were coated by the Ni powder. The results of electrochemical measurements show that the electrochemical catalytic property and exchange current density increased with raising of sinter temperature. The maximum discharge capacity increased first, then decreased with raising of sinter temperature, the peak value is about 466 mAh/g at 900 ℃, Moreover, the cyclic stability of the sintered electrodes was also improved.
V2.46TiFe0.54 alloy granules and Ni powder were mixed and pressed into electrodes greens, which were sintered at 850~1100 ℃ for 5 min. The influences of sinter temperature on the morphology and the electrochemical properties of the sintered V2.46TiFe0.54-Ni electrodes were investigated. XRD and SEM (EDS) analysises show that the V, Ti and Ni elements interdiffuse between the granules and Ni powders took places, resulting in forming a diffusing interlayer, its thickness increased with raising of the sintering temperature. The alloy granule surfaces were coated by the Ni powder. The results of electrochemical measurements show that the electrochemical catalytic property and exchange current density increased with raising of sinter temperature. The maximum discharge capacity increased first, then decreased with raising of sinter temperature, the peak value is about 466 mAh/g at 900 ℃, Moreover, the cyclic stability of the sintered electrodes was also improved.
2009, 38(6):1104-1107.
Abstract:
The laser sintering + isothermal forging technology was used to prepare excellent powder metallurgy TC17 titanium alloy, and the influence of technology on the microstructure and properties was investigated. The results indicated that the microstructure of laser sintered TC17 titanium alloy was comprised of coarse columnar β grains. After isothermal forging up and below β transus, followed by heat treatment, laser sintered Widmanst?tten structure was broken effectively, and transformed into plate, fine and equiaxed α phase. Only adopting isothermal forging below β transus and heat treatment, the microstructure consisted mainly of fine and equiaxed α phase, but little amount of primary β grain boundary was still remained owing to uniform deformation. After isothermal forging and heat treatment, the plasticity of the alloy at room temperature was increased obviously with little change of the strength, resulting in excellent match between strength and plasticity.
The laser sintering + isothermal forging technology was used to prepare excellent powder metallurgy TC17 titanium alloy, and the influence of technology on the microstructure and properties was investigated. The results indicated that the microstructure of laser sintered TC17 titanium alloy was comprised of coarse columnar β grains. After isothermal forging up and below β transus, followed by heat treatment, laser sintered Widmanst?tten structure was broken effectively, and transformed into plate, fine and equiaxed α phase. Only adopting isothermal forging below β transus and heat treatment, the microstructure consisted mainly of fine and equiaxed α phase, but little amount of primary β grain boundary was still remained owing to uniform deformation. After isothermal forging and heat treatment, the plasticity of the alloy at room temperature was increased obviously with little change of the strength, resulting in excellent match between strength and plasticity.
2009, 38(6):1108-1111.
Abstract:
The β-Ni(OH)2 nano-scale powder with needle-like and quasi-spheroshape was prepared by supersonic-assistant precipitation method using Tween-80 (C64H124O26-80) as dispersant. The prepared powder was added into micron-scale spheroshape nickel hydroxide at a ratio of 8% to get a combination electrode. Using the combination electrode as anode and LaNi5 alloy as cathode, the effect of Tw-80 dosage on the tap density of β-Ni(OH)2 and the discharge capability of the combination Ni electrode was studied. The result showed that both the tap density and the discharge capability increased at first, then decreased as the increase of dosage of Tw-80. The combination electrodes have a higher discharge voltage than the pure spheroshape Ni(OH)2. The maximum discharged capability with 256.75 mAh/g was obtained when the nanopowder with 2% dosage of Tw-80 was mixed with pure spheroshape Ni(OH)2 at a ratio of 8%. The capacity was 11.3% higher than that of the pure spheroshape Ni(OH)2 (230.7 mAh/g). Besides, the cycle life of the mixed electrode was also increased.
The β-Ni(OH)2 nano-scale powder with needle-like and quasi-spheroshape was prepared by supersonic-assistant precipitation method using Tween-80 (C64H124O26-80) as dispersant. The prepared powder was added into micron-scale spheroshape nickel hydroxide at a ratio of 8% to get a combination electrode. Using the combination electrode as anode and LaNi5 alloy as cathode, the effect of Tw-80 dosage on the tap density of β-Ni(OH)2 and the discharge capability of the combination Ni electrode was studied. The result showed that both the tap density and the discharge capability increased at first, then decreased as the increase of dosage of Tw-80. The combination electrodes have a higher discharge voltage than the pure spheroshape Ni(OH)2. The maximum discharged capability with 256.75 mAh/g was obtained when the nanopowder with 2% dosage of Tw-80 was mixed with pure spheroshape Ni(OH)2 at a ratio of 8%. The capacity was 11.3% higher than that of the pure spheroshape Ni(OH)2 (230.7 mAh/g). Besides, the cycle life of the mixed electrode was also increased.
2009, 38(6):1112-1115.
Abstract:
Nb-20Si, Nb-20Si-10W and Nb-20Si-10W-10Mo samples were prepared by a spark plasma sintering (SPS), the effects of W and W-Mo additions on the microstructure of Nb/Nb5Si3 composites were mainly investigated. The microstructures were examined by scanning electron microscope (SEM). X-ray diffraction (XRD) was used for phase identification of the samples. The compositions were analyzed by electron-probe micro-analysis (EPMA). Results indicate that Nb/Nb5Si3 composites up to 99.59% of theoretical density are fabricated. W can be perfect solid-solutioned in Nb/Nb5Si3 composites, and the microstructure of Nb/Nb5Si3 composites is not changed, but the microstructure of Nb/Nb5Si3 composites is obviously changed after addition of W-Mo, Nb monophase, the solid solution of W and Mo in Nb, and the solid solution of partial Nb in W appear, but the solid solution phenomena of Nb5Si3 is not detected.
Nb-20Si, Nb-20Si-10W and Nb-20Si-10W-10Mo samples were prepared by a spark plasma sintering (SPS), the effects of W and W-Mo additions on the microstructure of Nb/Nb5Si3 composites were mainly investigated. The microstructures were examined by scanning electron microscope (SEM). X-ray diffraction (XRD) was used for phase identification of the samples. The compositions were analyzed by electron-probe micro-analysis (EPMA). Results indicate that Nb/Nb5Si3 composites up to 99.59% of theoretical density are fabricated. W can be perfect solid-solutioned in Nb/Nb5Si3 composites, and the microstructure of Nb/Nb5Si3 composites is not changed, but the microstructure of Nb/Nb5Si3 composites is obviously changed after addition of W-Mo, Nb monophase, the solid solution of W and Mo in Nb, and the solid solution of partial Nb in W appear, but the solid solution phenomena of Nb5Si3 is not detected.
2009, 38(6):1116-1118.
Abstract:
The composite coatings on commercially pure titanium substrate were prepared by micro-arc oxidation (MAO) in electrolytic solution containing calcium acetate and β-glycerol phosphate disodium salt pentahydrate (β-GP) adopting the fixed anode voltage of 450 V and the oxidizing time of 5 min. The effects of cathode voltage on phase and composition morphology of MAO films were investigated. The results show that: the surface of MAO films are uniform and the components of the films are composed of TiO2 and Ca3 (PO4)2 while cathode voltage varies from 100 V to 200 V. When cathode voltage is 300 V, the surface of the MAO films are destroyed and the predominant component is CaTiO3.
The composite coatings on commercially pure titanium substrate were prepared by micro-arc oxidation (MAO) in electrolytic solution containing calcium acetate and β-glycerol phosphate disodium salt pentahydrate (β-GP) adopting the fixed anode voltage of 450 V and the oxidizing time of 5 min. The effects of cathode voltage on phase and composition morphology of MAO films were investigated. The results show that: the surface of MAO films are uniform and the components of the films are composed of TiO2 and Ca3 (PO4)2 while cathode voltage varies from 100 V to 200 V. When cathode voltage is 300 V, the surface of the MAO films are destroyed and the predominant component is CaTiO3.
2009, 38(6):1124-1128.
Abstract:
The research and development, preparation technologies, structures and properties of Mg-Ti binary alloys in the recent years are expatiated systematically. It is introduced that mechanical alloying method, physical vapor deposition (PVD) method, high pressure synthesis method and spark plasma sintering method can be used to obtain metastable Mg-Ti binary alloys. And the main factors affecting structural evolvement, hydrogen storage properties, switchable optical properties and mechanical properties of Mg-Ti binary alloys are analyzed. In addition, the pivotal problems in these researches are discussed and the development trend in the future is proposed.
The research and development, preparation technologies, structures and properties of Mg-Ti binary alloys in the recent years are expatiated systematically. It is introduced that mechanical alloying method, physical vapor deposition (PVD) method, high pressure synthesis method and spark plasma sintering method can be used to obtain metastable Mg-Ti binary alloys. And the main factors affecting structural evolvement, hydrogen storage properties, switchable optical properties and mechanical properties of Mg-Ti binary alloys are analyzed. In addition, the pivotal problems in these researches are discussed and the development trend in the future is proposed.
